1. Field of the Invention
This invention relates to liposomes and in particular to dehydrated liposomes which can be stored for extended periods of time and then rehydrated when and where they are to be used.
2. Description of the Prior Art
As is well known in the art, liposomes are closed vesicles having at least one lipid bilayer membrane surrounding an aqueous core. One of the primary uses for liposomes is as carriers for a variety of materials, such as, drugs, cosmetics, diagnostic reagents, bioactive compounds, and the like.
In connection with each of these uses, it is important to be able to store liposomes for long periods of time without substantial leakage from the liposomes of the selected materials they are carrying. More particularly, so as to be useful in commercial settings, liposome preparations must have long enough shelf-lives to allow them to be easily manufactured, shipped, and stored by intermediate and ultimate users under a variety of temperature conditions.
With particular regard to the drug industry, it is also important to be able to provide drug manufacturers with unloaded liposomes which the manufacturers can subsequently load in their own plants with their own drugs. Such a two step or two factory approach (i.e., manufacturing unloaded liposomes in a first plant and then filling them in a second plant) would allow drug manufacturers to purchase a defined commodity, i.e., unloaded liposomes, from suppliers and then use that commodity as an off-the-shelf component of their final product.
As drug manufacturers currently operate their businesses, they strongly prefer to buy defined commodities from suppliers and then assemble the final product in their own plants. In this way, they can personally control the quality of the finished products. Usage of liposome technology by the drug industry would be greatly enhanced if liposomes could also be provided to manufacturers as a defined commodity.
To date, liposome preparations have generally had relatively short shelf-lives. Moreover, there has been no known way to prepare liposomes at one point in time and then fill them with selected materials at a much later point in time. The present invention makes up for these existing shortcomings in the current state of the art.